Cellular origin of human lymphotoxin and its purification

Abstract

The ability of various subsets of human mononuclear cells to produce human lymphotoxin (LT) was examined. Peripheral blood mononuclear cells were separated into OKT4 +, OKT8 +, and Leu-lla + subpopulations by flow cytometry. Both OKT4 + and OKT8 + cells produced LT upon phytohemagglutinin (PHA) stimulation, but the OKT4 + T cells were the major source of LT. In contrast, Leu-lla + cells failed to produce LT. The LT production and the proliferative response to PHA, of OKT4 + and OKT8 + cells, were inhibited by prostaglandin E 2 and histamine. The LT, derived from PHA-stimulated peripheral blood lymphocytes, was purified by a procedure involving Blue-agarose, Con A-Sepharose chromatography, preparative gradient polyacrylamide gel electrophoresis and preparative sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The LT activity was recovered from SDS gel with major activity peak in the M rmr 76,000 region and the minor activity peak in the M rmr 24,000 region. The LT derived from 1788 lymphoblastoid cell line also showed heterogeneity on SDS gel. The activity was recovered from two peaks in the region of M rmr 70,000 and 20,000.